The present invention is directed to a fluid nozzle for providing a high velocity sheet of fluid of substantially uniform velocity, density and volume extending in a predetermined direction and arranged to impact a substrate to be treated by such sheet of fluid as the substrate is moved past the nozzle. In one form of the invention, it is directed to an improvement in a mass soldering system of the type described in the earlier patents of H.T. O'Rourke, U.S. Pat. Nos. 4410126 and 4401253. This prior patented system involves directing a hot air knife blast onto the bottom surface of a printed component-carrying circuit board, the air blast impinging on the surface immediately after the printed circuit board leaves a wave soldering system. The impinging air blast is reported to reduce the incidence of solder shorts, icicling and/or bridging, and has achieved widespread adoption.
In working with the previously patented system, various efforts have been made to improve the distribution of the air blast across the width of the path of travel of circuit boards through which the boards having the freshly deposited excess solder are passed for treatment by the air blast. In order to improve this uniformity, a modified tube construction has been suggested in the past to change the airflow characteristics. In one of these, a screen mesh baffle tube has been utilized inside of a round tube. While this has given some improvement, it has not given a substantially uniform flow of air across an orifice aimed at the solder to be removed.
In another form of the invention, the fluid knife is used as a cleaning system, particularly for removing soldering flux from surface mounted semiconductor components carried by printed circuit boards.